Machine gun



F. T. MOORE MACHINE GUN Dec. 20', 1938.

Filed Feb. 5, 1957 d 3 Sheets-Sheet l 2f' E I 05%/ t Urngy .Zz/z mentar v.FFEden/"aff 7'.' MDD @wwe F. T. MOORE 2,140,809

MACHINE GUN Filed Feb. s, 1937 5 sheets-sheet v2 trngy In Vani ar' ffsderfa'fr 72M Drs Dec. 20, 1938.

NW mm F. T. MOORE Dec. 20, 1938.

MACHINE GUN 3 sheets-snaai 34 Filed Feb. 3, 1957 I f77 m5771501 Ffsderfcffg'lfrs Patented Dec. `20, 1938 ITED STATS PATENT OFFICE MACHINE GUN ing Company, ,Y of Connecticut Hartford, Conn., a corporation Application February 3, 1937, Serial No. 123,875

10 Claims.

In a machine gun of the water cooled reciprocating barrel type, it is necessary to provide a packing near the front of the barrel to prevent leakage of cooling water or other coolant between 5 the moving barrel andthe adjacent portion of the barrel guide or jacket. It has heretofore been customary to provide a stuffing box at the front of the barrel, the packing being carried by the jacket and with the reciprocating barrel l .projecting through the stu'ing box and beyond the front of the jacket.

The conventional stuiiing box construction is objectionable for the reason that the front portion of the barrel, being beyond the jacket, is

l not subjected to the cooling action of the coolant,

and therefore becomes unduly heated. The excessive heating of the front portion may cause distortion of the barrel or changes in the characteristics of the meta-l with resultant excessive wear and inaccuracy of firing.

It is highly desirable that the packing be readily adjustable to compensate for wear thereof, and it is further desirable that such adjustment be conveniently possible without any disassembly of the essential parts of the gun.

An important object of the present invention is to provide a construction wherein the packing is readily adjustable and is so positioned and so related to other parts that the entire forward portion of the barrel is subject to cooling action.

In automatic machine guns of the reciprocating barrel type provision has heretofore been made to accelerate the rate of iire by means of an apertured plug or disc at the front of the 5 barrel, thus providing a gas chamber at the front of the barrel so that the gases of explosion can react upon the barrel to increase the speed of recoil. In a gun thus provided with a gas reaction chamber there is an even greater tendency for the front end portion of the barrel to become unduly heated, if the barrel projects in. the conventional manner at the front of the coolant jacket.

A further object of the present invention is to provide a gun having a gas reaction chamber for accelerating the rate of fire and having the end portion of the barrel against which the gases react so related to the coolant jacket that the said end portion is at all times subjected to effective cooling action.

Other objects of the invention will be apparent from the following specication andr claims.

In the accompanying drawings I have shown two suitable embodiments of the invention, but it will be understood that the drawings are intended for illustrative purposes only and are not to be construed as dening or limiting the scope of the invention, the claims forming a part ofthis specification being relied upon for that purpose.

Of the drawings: '5

Fig. 1 is a fragmentary side View of the front portion. of a machine gun embodying the invention, parts of the jacket and associated elements being shown in central longitudinal section.

Fig. 2 is an enlarged fragmentary view of the 10 front end portion of the barrel partly in longitudinal section.

Figs. 3 and 4 are enlarged side and end views respectively of the packing adjusting ring.

Fig. 5 is an enlarged rear view of the barrel 15 guide.

Fig. 6 is a fragmentary view similar to the forward portion of Fig. 1 but showing an alternative embodiment of the invention.

Figs. 7 and 8 are central longitudinal sectional 20 views showing respectively the forward and rear portions of an alternative machine gun embodying the invention.

Fig. 9 is an enlarged fragmentary side view of the rear portion of the barrel shown in Figs. 7 S25 and 8.

Fig. 10 is an enlarged fragmentary longitudinal sectional view showing the forward portion of the barrel and jacket and the elements immediately associated therewith.

Fig. 11 is an enlarged vertical transverse sectional view taken along the line ll-I l of Fig. 10, the barrel and certain other elements being omitted.

Figs. 12 and 13 are enlarged side and end views 35 respectively of the flange or piston carried by the barrel.

Figs. 14 and l5 are enlarged side and end views respectively of the packing adjusting ring.

Fig. 16 is an enlarged side and sectional View of 40 the plug forming a gas chamber at the front of the barrel.

Fig. 17 is an end view of the plug shown in Fig. 16.

In Fig. 1 of the drawings I have shown the for- 45 ward portion of a machine gun which as to details of construction may be similar to that shown in the patent to John M. Browning No. 1,293,021, but it will be understood that the invention is not so limited. The gun comprises a casing I within 50 which the gun mechanism isl contained, and it also comprises a reciprocating barrel 2 operatively connected with the said mechanism and. extending forward at the front of the casing. Secured to the casing and extending forward therefrom is a coolant jacket 3 which surrounds the barrel and is adapted to contain water or other suitable liquid coolant.

The coolant jacket 3 is provided with a front end wall 4 which is so positioned Vthat substantially all of the barrel when in its foremost position is behind the rear piane of the said wall. Preferably all of the barrel including the front face thereof is behind the said plane. A cylindrical barrel guide 5 is carried by the end wall 4 at an aperture therein. rearward into the interior of the jacket and it preferably has a threaded connection with the end wall. The guide 5 preferably has an inclined lip 5a for facilitating entry of the barrel 2 into the guide.

In order to prevent leakage Yof the water or other coolant outward through the barrel guide and around the barrel a suitable packing 6 is provided, which is carried by and movable with the barrel. As shown the forward end portion of the barrel is reduced in diameter to provide an annular space for receiving the packing. The

packing 6 is formed from a suitable resilient packing material and it engages the interior surface of the guide 5 to prevent leakage. For holding the packing 6 in place and for adjusting it to compensate for wear, there is provided an adjusting ring 'I. This ring I is immediately adjacent the packing at the front thereof and it has threaded engagement with the barrel. The annular walls on the barrel and on the ring are preferably inclined so as to more effectively hold the packing in place. It will be apparentf that rotation of the ring will cause the packing 6 to be compressed and expanded so as to properly engage the interior surface of the guide. The

Yring 'I is provided with suitable means such as notches 8, 8 which enable the ring to be conveniently engaged by a wrenchto facilitate adjustment. Y

It will be apparent that inasmuch as the external diameter of the adjusting ring and of the packing are approximately the same as the external diameter of the front portion of the barrel, it is possible to Withdraw the barrel rearward in the usual manner for purposes of disassembling. When the gun is reassembled the barrel is moved forward, the lip 5a serving to guide it into the central bore of the guide 5.

Inasmuch as the guide 5 is positioned entirely Within the jacket 3 so as to be surrounded by the coolant and inasmuch as the forward end portion of the barrel together with the packing 6 and the adjusting ring 'I are positioned in the main within the guide, it will be apparent that excessive heating of any portion of the barrel is prevented. By the construction and arrangement shown I avoid the projection of any portion of the barrel beyond the cooling Zone, and at the same time I provide for a convenient adjustment of the packing at any time without disassembling any major parts of the gun.

In Fig. 6 I have shown a construction very similar to that shown in Fig. ibut differing slightly in that the jacket 3 is longer so that the front end portion of the barrel together with the packing and the adjusting ring are even more effectively cooled. Except for the longer jacket, the 'parts shown in Fig. 6 are the same as those shown in Fig. 1, and repetition of the description is therefore unnecessary.-

A machine gun of the type represented in Figs. 1 to 6 is shown in greater detail in Figs. '7 to i7. The said gun comprises a-breech casing Iii which The guide 5 projects contains the breech mechanism, this casing being rectangular in form and having two side plates Il connected at the front with a trunnion block I2 by riveting or otherwise. The rear part of the bottom of the casing is closed by a transverse bottom plate I3 and the rear part of the top of the casing is closed by the top plate I 4. In front of the plate I4 there is provided a cover I5 pivoted at I6 so that it can be swung upward to expose the interior parts. The casing is closed at the rear by means of a plate Il which is vertically movable in grooves (not shown) formed in the two side plates II. The plate Il is held in place by a manually releasable pivoted latch I 8. The plate l'I carries a buffer mechanism indicated as an entirety by I9.

Projecting from the casing at the front is a barrel 2l) which upon recoil is movable rearward to a limited extent. The barrel extends through a hole ZI in the trunnion block I2, the front portion Z Ia of the said hole being considerably larger than the barrel and the rear portion 2 Ibofthehole fitting or approximately fitting the rear portion 26a of the barrel and providing a bearing therefor. The barrel has another bearing at or near the forward end of a barrel jacket 22, the said jacket being carried by a flange 23 formed on the trunnion block. This last said bearing will be presently described indetail.

Connected with the barrel 2i? at the rear end thereof and bodily movable therewith is a barrel extension 26. This barrel extension comprises two integrally formed side members connected at the front by a cross member 24a which is recessed and threaded for engagement with the threaded rear end of the barrel. 'Ihe said barrel preferably has notches 25, 25 adapted to be engaged by a spring detent 26 on the extension for normally holding the barrel against rotation.

Mounted on the barrel extension for longitudinal movement independently thereof is a breech bolt 21. This breech bolt is provided at its opposite sides with longitudinal tongues 27a adapted to enter longitudinal grooves formed in the side members of the barrel extension. action spring 28 is provided which extends into a longitudinal opening 29 in the breech bolt and Which tends to hold the breech bolt in its forward position. Upon recoil this reaction spring is compressed and immediately tends to return the breech bolt in the forward direction.

Mounted in the rear lower part of the casing is a lock frame 35 comprising two side members lying closely adjacent the side walls Ii of the casing. Immediately in front of the lock frame Sii is a transverse block SI secured to the bottom wall I3. When the parts are in their forward positions as shown in Fig. 8 the breech bolt is locked to the barrel extension by means of a lock bolt 32 vertically movable in a recess in the rear transverse portion 24h of the barrel extension and entering a notch in the breech bolt. The lock 32 is held in its upper locking position by means of the transverse block 3l, but when the barrel extension and breech bolt move rearward, the said lock bolt is moved downward by means of cam surfaces t3 formed at the forward ends of the lock frame Sil. This permits the breech bolt to move rearward independently of the barrel extension. When the parts are returned to their forward positions the lock bolt 32 is again moved to locking position by means of the cam surfaces 311i on the block 3I.

Transversely pivoted on the lock frame 38 is a rock lever or accelerator 35 having a convex 'In forward facing'surface adaptedto be engaged by the rear surface of the barrel extension. When the barrel extension moves rearward upon recoil the breech bolt is unlocked therefrom in the manner already described and the accelerator is moved in the counter-clockwise direction. The upper end of the accelerator engages the surface 36 on the breech bolt and the accelerator thus serves to assist or accelerate the rearward movement of the bolt, acting as a means for transmitting the energy of the relatively heavy barrel extension and barrel to the lighter breech bolt.

Pivotally mounted on the breech bolt at the left side thereof is an extractor 3l. The extractor is controlled by suitable cams which are not fully shown, inasmuch as the details of the extractor and its operating means constitute no part of the present invention. As the breech bolt moves rearward the extractor withdraws a cartridge from the feed mechanism 45.3 at the front. The extractor moves the cartridge rearward and downward so that, upon the return movement of the breech bolt, the cartridge is pushed into the firing chamber at the rear end of the barrel ready to be fired.

The firing mechanism is not shown in detail as it does not as to its details constitute any part of the present invention. Firing is effected by means of a trigger 38 acting through a lever 39.

The entire gun mechanism within the casing will for the sake of brevity be hereinafter referred to as mechanism serving to effect feeding and firing.

The jacket 22 serves to hold a body of water or other coolant which surrounds the barrel throughout substantially its entire length so as to prevent the barrel from overheating when the gun is in use. Mounted within the jacket is a steam tube 4l of known construction, this having two ports therein either of which may be automatically closed by a sleeve 42 slidable longitudinally in accordance with the direction of inclination of the gun. A- steam discharge duct 43, more clearly shown in Fig. 1l, is connected with the front end of the tube.

As will be observed in Fig. '7, the coolant extends rearward around the barrel into the larger front portion Ela of the hole in the trunnion block. The water extends rearward so as to surround the zone adjacent the front end of the cartridge chamber, which Zone tends to become greatly heated if ring is continued throughout an extended period. As already stated, the rear portion 20a of the barrel approximately fits the rear portion 2 lb of the hole in the trunnion block, but in order to prevent leakage of water or other coolant rearward into the casing I preferably provide a packing construction such as disclosed and claimed in my copending application for Machine gun with adjustable packing, Serial No. '7,129 led February 18, 1935.

An annular packing 44 is provided on the barrel and in engagement with the inner surface of the hole 2lb. In order that the packing 44 may be adjusted so as to make it initially tight and so as to compensate for wear, there is provided an adjusting means which is adjacent the packing and movable with the barrel. This means is preferably an annular ring 45 which is in threaded engagement with the barrel and which can be rotated on its threads to cornpress and expand the packing to the extent desired. The ring 45 is provided with holes 4E to facilitate engagement of the ring and rotation thereof by means of a Spanner wrench. The annular walls on the barrel and on the ring adjacent the packing are preferably inclined so as to more effectively hold the packing in place.

Preferably the barrel at the rear of the packing 44 and the ring 45 is of approximately the same diameter as at the front of the packing, and the said packing and the said ring are therefore positioned in an annular groove in the barrel. The ring 45 is preferably integral and continuous, and the portion of the barrel at the rear of the ring, therefore, preferably consists of a second ring 41, which is permanently secured to the main body of the barrel.

As already stated, the barrel and the barrel extension are reciprocable. They move rearward from the position shown in Fig. 7 upon the ring of each cartridge and are automatically returned after the automatic extracting of the empty cartridge shell and the automatic feeding of a new cartridge into position to be pushed into the chamber, During this automatic movement the packing 44 remains within the hole 2lb in the trunnion block, thus preventing leakage for all positions of the barrel. In order to economize space and to locate the packing 44 as far to the rear as possible, the ring 45 is made relatively narrow and is so positioned that it is normally substantially entirely concealed Within the hole 2lb, as shown in Fig. 7.

Adjustment of the packing by rotating the ring 45 may be effected with the barrel entirely removed from the gun and detached from other parts or with the barrel and barrel extension withdrawn rearward and removed from the gun in assembled relationship as set forth in the said Browning patent. Preferably, however, the packing adjusting means is so arranged as to be accessible for adjustment from the exterior of the gun with the barrel extension in the casing and with the barrel in normal engagement with the extension.

When the barrel is moved sufficiently rearward from the position shown in 7, a portion of the ring 45 is exposed at the rear of the trunnion block so as to permit access to be had to the holes 48, 4B. Thus, by operating the mechanism of the gun manually and retaining it in the rearward position, the ring 45 is exposed suiiiciently to permit adjustment-thereof. It will be understood that in adjusting the ring the cover l5 is raised and access to the ring is had through the resultant opening in the top of the gun.

In order to increase the rate of ring a gas reaction chamber 48 may be provided entirely at the front of the barrel, this chamber being entirely within a guide 49, corresponding to the guide 5 already described. In order that access may conveniently be had to the barrel from the front, a removable disk or plug 5) is provided which is threaded into the forward portion of the guide 49. The plug Ell constitutes the front wall of the gas chamber and it has a central aperturel of sufficient size to permit the free passage of the bullets. The plug is preferably formed at the front with a hexagonal portion 52 to facilitate engagement by a wrench.

'Ille rate of firing may be still further increased by enlarging the guide 49 and by providing a flange or piston 53 on the barrel near the front thereof of such size as to fit the interior of the guide. This ange or piston may be formed integrally with the barrel but preferably it is structurally separate and connected by threads as shown in detail in Fig. 10. The piston 53 preferably has a substantially flat rear face.

When a flange or piston such as 53 is provided the packing for preventing leakage ofcoolant at the front is mounted on the piston 53, instead of being mounted directly on the barrel as shown in Figs. 1 and 2. The packing is shown at 54 being similar to the packing 6 already described. This packing is closely adjacent the rear substantially flat face of the piston. Adjacent the packing 5l! and at the front thereof is an adjusting ring 55 corresponding in function to the ring 'l already described. The ring 55 is provided with notches 5E, 5% adapted to be engaged by a special wrench to facilitate adjustment. It is contemplated that a wrench may be provided which will permit adjustment of the ring 55 when the plug 5B has been removed and with the other parts remaining in the relative positions shown in Fig. l0.

It will be understood that upon firing, the explosive gases enter the gas reaction chamber 48 and greatly increase the speed of recoil of the barrel. In this way the barrel is provided with additional energy which is transferred through the barrel extension and the accelerator 55 so as to increase the speed of rearward movement of the breech bolt 27. The increased speed of rearward movement of the bolt causes increased energy to be absorbed by the reaction spring 23 which may, if necessary, be of greater than normal size. Thus the breech bolt is returned in the forward direction at an increased speed. It will be evident that as the result of all of the foregoing the entire cycle of operations is speeded up, thus considerably accelerating the rate of fire.

From an inspection of the drawings, particularly Fig. 10, it will be apparent that the forward portion of the barrel, together with the piston and other parts carried thereby, and also the gas chamber itself, are entirely surrounded by the water or other coolant in the jacket 22. In view of the fact that the piston is substantially flat at the rear, the coolant can enter the rear portion of the guide and thus cool the pis-- ton and the packing carried thereby. Thus I entirely avoid any deleterious effects which would result from excessive heating of the front portion of the barrel and associated parts.

What I claim is:

i. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that substantially all of the barrel when in its foremost position is behind the rear plane of the said wall, an annular packing carried by the barrel near and at the rear of the front end thereof, a thin-walled cylindrical guide within the jacket surrounding and closely fitting the packing, the said guide projecting rearward from the said front jacket wall and having its entire periphery spaced from the outer jacket wall, and an adjusting ring on the barrel adjacent the front of the packing, the said ring having threaded connection with the barrel and being accessible at the front of the jacket so that it may be turned to adjust the packing.

2. In a machine gun, the combination of a casing, a longitudinally lreciprocating integral barrel at the front of the casing, a coolant jacket extending forward from the casing ,and surrounding the barrel and having its front wall so positioned that substantially all of the barrel when in its foremost position s behind the rear plane of the said wall, an annular packing carried by the barrel near and at the rear of the front end thereof which packing has approximately the same external diameter as the barrel, a thin-walled cylindrical guide within the jacket surrounding and closely fitting the barrel and the packing, the said guide projecting rearward from the said front jacket wall and having its entire periphery spaced from the outer jacket wall, and an adjusting ring on the barrel adjacent the front of the packing and having approximately the same external diameter as the barrel and the packing, the said ring having threaded connection with the barrel and being accessible at the front of the jacket so that it may be turned to adjust the packing. V

3. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, the said barrel having thereon near the front end thereof a cylindrical piston of larger diameter than the main body of the barrel which piston has a substantially at rear face, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that substantially all of the barrel when in its foremost position is behind the rear plane of the said wall, anv annular packing carried by the piston .near the said flat rear face thereof, a thin-walled cylindrical guide within the jacket surrounding and closely fitting the piston and the packing, the said guide projecting rearward from the said front jacket wall of the jacket and having its entire periphery spaced from the outer jacket wall and the said guide being open at the rear to permit coolant to contact with the rear face of the piston and with the portion of the barrel immediately behind the piston, and an adjusting ring on the piston adjacent the front of the packing and having threaded connection with the piston, the said ring being accessible at the front of the jacket so that it may be turned to adjust the packing.

4. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, the said barrel having thereon near and at the rear of the front end thereof a cylindrical piston of larger diameter than the main body of the barrel which piston has a substantially at rear face, a coolant jacket extending forward from the casing and surrounding the barrel and having its fron-t wall so positioned that its rear plane is in front of the front face of the barrel when the barrel is in its foremost position, an annular packing carried by the piston near the said flat rear face thereof, a thin-walled cylindrical guide within the jacket surrounding and closely fitting the piston and the packing, the said guide projecting rearward from the said front jacket wall and having its entire periphery spaced from the outer jacket wall and the said guide being open at the rear to permit coolant to contact with the rear face of the piston and with the portion of the barrel immediately behind the piston, and an adjusting ring adjacent the front of the packing and having threaded connection with the piston, the said ring being always entirely behind the said rear plane of the front jacket wall and being accessible at the front of the jacket so that it may be turned to adjust the packing.

5. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, a cylindrical piston structurally separate from the barrel and carried thereby near the front end thereof, the

said piston being of larger diameter than the adjacent portion of the barrel and having a substantially iiat rear face, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that the said piston and substantially all of the barrel are behind the'rearplane of the said wall when the barrel is in its foremost position, an annular packing carried by the piston near the said rear face thereof, thin-walled cylindrical guide within the jacket surrounding and closely fitting the piston and the packing, the said guide projecting rearward from the said front jacket wall and having its entire periphery spaced from the outer jacket wall and the said guide being open at the rear to permit coolant to contact with the rear face of the piston and with the portion of the barrel immediately behind the piston, and an adjusting ring on the piston positioned adjacent the front of the packing and having threaded connection with the piston, the said ring being accessible at the front of the jacket so that it may be turned to adjust the packing.

6. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, mechanism in the casing operated by the rearward recoil moveyment of the barrel and serving to effect feeding and firing, a coolant jacket extending forward from the casing and. surrounding the barrel and having its front wall so positioned that its rear plane is in front of the front face of the barrel when the barrel is in its foremost position, a thinwalled cylindrical guide within the jacket carried by the said front wall thereof and surrounding the barrel, an annular packing cooperating with the guide and the barrel to prevent the escape of c-oolant at the front, and a centrally apertured means forming a gas reaction chamber entirely at the front of the barrel and entirely within the barrel guide behind the said rear plane of the front jacket wall, the said reaction chamber enabling gases of explosion to react upon the front face of the barrel so as to cause increased recoil and thereby cause operation of the aforesaid mechanism at an increased speed.

'7. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, mechanism in the casing operated by the rearward recoil movement of the barrel and serving to effect feeding and firing, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that its rear plane is in front of the front face of the barrel when the barrel is in its foremost position, an annular packing carried by the barrel near and at the rear of the front end thereof, a cylindrical guide within the jacket carried by the said front jacket Wall and surrounding and closely fitting the packing, an adjusting ring adjacent the front of the packing and having threaded connection with the barrel, and a centrally apertured plug at the front of the guide and removable to permit access to the ring so that it may be turned and adjusted, the said plug cooperating with the barrel guide to form a gas reaction chamber which is entirely at the front of the barrel and entirely within the guide and behind the said rear plane of the front jacket wall and which enables gases of explosion to react upon the front face of the barrel so as to cause increased recoil and thereby cause operation of the afore said mechanism at an increased speed.

8. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrelat the front of the casing, vmechanism in the casing operated by the rearward recoil movement of the barrel and serving to effect feeding and ring, the said barrell having thereon near the front end thereof acylindrical piston of larger diameter than the main body of the barrel, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that its rear plane is in front of the front face of the barrel when the barrel is in its foremost position, a cylindrical guide within the jacket carried by the front wall thereof and surrounding the barrel, an annular packing cooperating with the guide and barrel to prevent the escape of coolant at the front, and a centrally apertured Imeans cooperating with the barrel guide to form a gas reaction chamber entirely at the front of the barrel and piston and entirely within the guide behind the said rear plane of the front jacket wall, the said reaction chamber enabling gases of explosion to react upon the front face of the piston so as to cause increased recoil and thereby cause operation of the aforesaid mechanism at an increased speed.

9. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, mechanism in the casing operated by the rearward recoil movement of the barrel and serving to effect feeding and firing, the said barrel having thereon near the front end thereof a cylindrical piston of larger diameter than the main body of the barrel which piston has a substantially flat rear face, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that its rear plane is in front of the front face of the barrel when the barrel is in its foremost position, an annular packing carried by the piston near the said rear face thereof, a cylindrical guide within the jacket carried by the said front wall thereof and surrounding and closely fitting the piston and the packing, the said guide being open at the rear to permit coolant to contact with the rear face of the piston and with the portion of the barrel immediately behind the piston, and a centrally apertured means cooperating with the barrel guide to form a gas reaction chamber entirely at the front of the barrel and piston and entirely within the guide behind the said rear plane of the front jacket wall, the said reaction chamber enabling gases of explosion to react upon the front face of the piston so as to cause increased recoil and thereby cause operation of the aforesaid mechanism at an increased speed.

10. In a machine gun, the combination of a casing, a longitudinally reciprocating integral barrel at the front of the casing, mechanism in the casing operated by the rearward recoil movement of the barrel and serving to effect feeding and firing, the said barrel having thereon near the front end thereof a cylindrical piston of larger diameter than the main body of the barrel which piston has a substantially flat rear face, a coolant jacket extending forward from the casing and surrounding the barrel and having its front wall so positioned that its rear plane is in front of the front face of the barrel when the barrel is in its foremost position, an annular packing carried by the piston near the said rear face thereof, a cylindrical guide within the jacket carried by the said front Wall thereof and surrounding and closely tting the piston and the packing, an adjusting ring adjacent the front of the packing and having threaded connection with the piston, and a centrally apertured plug at the front of the guide and removable to permit access to the ring so that it may be turned and adjusted, the said plug vcooperating with the barrel guide to form a gas reaction chamber which is entirely at the front of the barrel and piston and entirely Within the guide behind the said rear plane of the front jacket Wall and which enables gases of explosion to react upon the front face of the piston so as to cause increased recoil and thereby cause voperation of the aforesaid mechanism at an increased speed.

FREDERICK T. MOORE. 

